CN113540425A

CN113540425A - Negative electrode material, and electrochemical device and electronic device comprising same

Info

Publication number: CN113540425A
Application number: CN202110804929.XA
Authority: CN
Inventors: 姜道义; 陈志焕; 崔航; 谢远森
Original assignee: Ningde Amperex Technology Ltd
Current assignee: Ningde Amperex Technology Ltd
Priority date: 2019-08-07
Filing date: 2019-08-07
Publication date: 2021-10-22
Anticipated expiration: 2039-08-07
Also published as: CN113540425B; EP3963649A1; JP7274601B2; US20220158176A1; CN110444750A; WO2021022821A1; EP3963649A4; CN110444750B; JP2022528111A

Abstract

The present application relates to an anode material, and an electrochemical device and an electronic device including the same. The anode material comprises a lithiated silica material, an inorganic coating layer and a polymer coating layer, wherein the inorganic coating layer and the lithiated silica material at least have Si-O-M bonds, and M comprises at least one of an aluminum element, a boron element and a phosphorus element. The cathode material has high stability to water, high first coulombic efficiency and good cycling stability.

Description

Negative electrode material, and electrochemical device and electronic device comprising same

The present application is a divisional application of an invention patent application having an application date of 2019, 8/7/No. 201910725660.9 and having an invention name of "a negative electrode material and an electrochemical device and an electronic device including the same".

Technical Field

The application relates to the field of energy storage, in particular to a negative electrode material, an electrochemical device and an electronic device comprising the same, and particularly relates to a lithium ion battery.

Background

The silicon-oxygen cathode material is most likely to be the cathode material of the next generation lithium ion battery because of its gram capacity of 1500-1800mAh/g and relatively low volume expansion (< 160%). However, the first coulombic efficiencies, which are generally below 75%, are currently important reasons limiting their application. The pre-lithiation treatment of the silicon-oxygen negative electrode material can increase the first coulombic efficiency of the lithium ion battery containing the pre-lithiated silicon-oxygen negative electrode material to more than 88%, and thus, the lithium ion battery has been widely studied in the industry. However, pre-lithiation has a certain effect on the stability of the silicon-oxygen negative electrode material, and particularly in the processing of aqueous slurries, the slurries are susceptible to gas generation and gelation. The current solution is mainly to modify the surface of the material to improve the water-resistant stability of the pre-lithiated silica negative electrode material. The main modification method is to improve the water-resistant stability of the material surface by using some hardeners (such as metal salts and inorganic acid salts) or some lithium ion shielding agents, and the methods can relieve the hydrolytic collapse of the silicate to a certain extent, but still cannot fundamentally solve the hydrolysis problem of the silicate. Thus, the water-resistant stability of the prelithiated silicone materials needs to be further improved.

Disclosure of Invention

Embodiments of the present application provide an anode material and a method of preparing the anode material in an attempt to solve at least one of the problems existing in the related art to at least some extent. The embodiment of the application also provides a negative electrode containing the negative electrode material, an electrochemical device and an electronic device.

In one embodiment, the present application provides an anode material comprising a lithiated silica material, an inorganic coating layer, and a polymer coating layer, wherein the inorganic coating layer has at least a Si-O-M bond with the lithiated silica material, wherein M includes at least one of an aluminum element, a boron element, and a phosphorus element.

In another embodiment, the present application provides an anode comprising an anode material according to embodiments of the present application.

In another embodiment, the present application provides an electrochemical device comprising an anode according to embodiments of the present application.

In another embodiment, the present application provides an electronic device comprising an electrochemical device according to an embodiment of the present application.

Additional aspects and advantages of embodiments of the present application will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of embodiments of the present application.

Drawings

Drawings necessary for describing embodiments of the present application or the prior art will be briefly described below in order to describe the embodiments of the present application. It is to be understood that the drawings in the following description are only some of the embodiments of the present application. It will be apparent to those skilled in the art that other embodiments of the drawings can be obtained from the structures illustrated in these drawings without the need for inventive work.

Fig. 1 shows a schematic structural diagram of an anode material of an embodiment of the present application.

Fig. 2A is a Scanning Electron Microscope (SEM) picture of the surface of the negative electrode material of comparative example 3 of the present application; fig. 2B is an SEM picture of the surface of the negative electrode material of comparative example 2 of the present application; fig. 2C is an SEM picture of the surface of the anode material according to example 12 of the present application; fig. 2D is a cross-sectional SEM picture of the anode material of example 12 of the present application.

Fig. 3A shows the appearance of an aqueous slurry made of the negative electrode material of comparative example 3 of the present application after leaving for 48 hours; fig. 3B shows the appearance of an aqueous slurry made of the anode material of example 12 of the present application after leaving for 48 hours.

Fig. 4 shows the cycle decay curves of the lithium ion batteries of comparative example 2, comparative example 3 and example 12 of the present application, respectively.

Detailed Description

Embodiments of the present application will be described in detail below. The embodiments of the present application should not be construed as limiting the present application.

As used in this application, the term "about" is used to describe and illustrate minor variations. When used in conjunction with an event or circumstance, the terms can refer to instances where the event or circumstance occurs precisely as well as instances where the event or circumstance occurs in close proximity. For example, when used in conjunction with numerical values, the term can refer to a range of variation that is less than or equal to ± 10% of the stated numerical value, such as less than or equal to ± 5%, less than or equal to ± 4%, less than or equal to ± 3%, less than or equal to ± 2%, less than or equal to ± 1%, less than or equal to ± 0.5%, less than or equal to ± 0.1%, or less than or equal to ± 0.05%.

Additionally, amounts, ratios, and other numerical values are sometimes presented herein in a range format. It is to be understood that such range format is used for convenience and brevity, and should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited.

In the detailed description and claims, a list of items connected by the terms "one of," "one of," or other similar terms may mean any one of the listed items. For example, if items a and B are listed, the phrase "one of a and B" means a alone or B alone. In another example, if items A, B and C are listed, the phrase "one of A, B and C" means only a; only B; or only C. Item a may comprise a single element or multiple elements. Item B may comprise a single element or multiple elements. Item C may comprise a single element or multiple elements.

In the detailed description and claims, a list of items linked by the term "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items a and B are listed, the phrase "at least one of a and B" means a only; only B; or A and B. In another example, if items A, B and C are listed, the phrase "at least one of A, B and C" means a only; or only B; only C; a and B (excluding C); a and C (excluding B); b and C (excluding A); or A, B and C. Item a may comprise a single element or multiple elements. Item B may comprise a single element or multiple elements. Item C may comprise a single element or multiple elements.

First, negative electrode material

The embodiment of the application provides an anode material, including: the lithium-containing silicon oxide material comprises a lithium-containing silicon oxide material, an inorganic coating layer and a polymer coating layer, wherein the inorganic coating layer and the lithium-containing silicon oxide material at least have Si-O-M bonds, and M comprises at least one of aluminum elements, boron elements and phosphorus elements.

In some embodiments, the lithiated silica material includes Li therein₂SiO₃、Li₆Si₂O₇、Li₂Si₂O₅And Li₄SiO₄At least one of (1).

In some embodiments, the inorganic coating layer includes a compound containing at least one of a phosphorus element, an aluminum element, and a boron element.

In some embodiments, the phosphorus element-containing compound is derived from at least one of phosphoric acid, tripolyphosphoric acid, sodium tripolyphosphate, and potassium tripolyphosphate.

In some embodiments, the compound containing an elemental aluminum is derived from one or more of sodium metaaluminate, potassium metaaluminate, aluminum trichloride, and aluminum hydroxide.

In some embodiments, the compound containing elemental boron is derived from one or more of the following: boric acid, sodium tetraborate or a hydrate thereof, potassium tetraborate or a hydrate thereof, sodium metaborate or a hydrate thereof and potassium metaborate or a hydrate thereof.

In some embodiments, the compound containing any combination of elemental phosphorus, elemental aluminum, and elemental boron is derived from one or more of aluminum dihydrogen tripolyphosphate, aluminum phosphate, aluminum borate, and aluminum tetrahydroborate.

In some embodiments, the weight percentage of M is about 0.05 wt% to 1.0 wt% based on the total weight of the anode material. In some embodiments, the weight percentage of M is about 0.05 wt% to 0.9 wt% based on the total weight of the anode material. In some embodiments, the weight percentage of M is about 0.06 wt%, about 0.07 wt%, about 0.08 wt%, about 0.1 wt%, about 0.2 wt%, about 0.4 wt%, about 0.6 wt%, or about 0.8 wt%, based on the total weight of the anode material.

In some embodiments, the negative active material has an X-ray diffraction peak with a 2 θ value of about 21.7 ± 1 °.

In some embodiments, the polymer coating comprises a hydrophobic polymer.

In some embodiments, the polymer coating comprises at least one of the following compounds: polyimide, polyamideimide, polysiloxane, poly (styrene-butadiene rubber), epoxy resin, polyester resin, and polyurethane resin.

In some embodiments, the weight percentage of the polymer coating layer is about 0.1 wt% to 10 wt% based on the total weight of the anode material. In some embodiments, the weight percentage of the polymer coating layer is about 0.5 wt% to 9 wt% based on the total weight of the anode material. In some embodiments, the weight percentage of the polymer coating layer is about 1 wt% to 8 wt% based on the total weight of the anode material. In some embodiments, the weight percentage of the polymer coating layer is about 2 wt% to 7 wt% based on the total weight of the anode material. In some embodiments, the weight percentage of the polymer coating layer is about 3 wt% to 5 wt% based on the total weight of the anode material.

In some embodiments, the polymer cladding layer has a thickness of about 5nm to 200 nm. In some embodiments, the polymer cladding layer has a thickness of about 10nm to 150 nm. In some embodiments, the polymer cladding layer has a thickness of about 20nm to 100 nm. In some embodiments, the polymer cladding layer has a thickness of about 30nm to 80 nm.

In some embodiments, the lithiated silica material includes nanocrystalline silicon grains having a grain size of no greater than about 10 nm. In some embodiments, the nano-silicon grains have a grain size of no greater than about 8 nm. In some embodiments, the nano-silicon grains have a grain size of no greater than about 5 nm.

Fig. 1 shows a schematic structural diagram of an anode material of an embodiment of the present application. Wherein the inner layer 1 is lithiated silica material, the intermediate layer 2 is inorganic coating layer, and the outer layer 3 is polymer coating layer.

Preparation method of anode material

An embodiment of the present application provides a method for preparing any one of the above-mentioned anode materials, including:

(1) adding the pre-lithiated silica material and an inorganic coating material into a solvent to form a suspension, and filtering and drying to obtain a pre-lithiated silica material with the surface coated by the inorganic coating layer; and

(2) and adding the obtained pre-lithiated silica material with the surface coated by the inorganic coating layer and the polymer into a solvent to form a mixed solution, removing the solvent, and heating at the temperature of about 50-300 ℃ for about 4-12 hours to obtain the negative electrode material.

In some embodiments, the inorganic coating material comprises at least one of the following materials: phosphoric acid, tripolyphosphoric acid, sodium tripolyphosphate, potassium tripolyphosphate, sodium metaaluminate, potassium metaaluminate, aluminum trichloride, aluminum hydroxide, boric acid, sodium tetraborate or a hydrate thereof, potassium tetraborate or a hydrate thereof, sodium metaborate or a hydrate thereof, potassium metaborate or a hydrate thereof, aluminum dihydrogen tripolyphosphate, aluminum phosphate, aluminum borate, and aluminum tetrahydroborate.

In some embodiments, the solvent comprises at least one of the following compounds: ethanol, toluene, xylene, N-methylpyrrolidone, tetrahydrofuran, acetone, dimethylformamide, dimethylacetamide, dimethyl ether, and butanol.

In some embodiments, the drying temperature is about 50-100 ℃. In some embodiments, the drying temperature is about 60-90 ℃. In some embodiments, the drying temperature is about 70 ℃ or about 80 ℃.

In some embodiments, the polymer comprises a hydrophobic polymer. In some embodiments, the polymer comprises at least one of the following compounds: polyimide, polyamideimide, polysiloxane, poly (styrene-butadiene rubber), epoxy resin, polyester resin, and polyurethane resin.

In some embodiments, the heating temperature is about 100-. In some embodiments, the heating temperature is about 80-200 ℃. In some embodiments, the heating temperature is about 150-.

In some embodiments, the heating time is about 5-10 hours. In some embodiments, the heating time is about 6 hours, about 7 hours, about 8 hours, or about 9 hours.

The silicon-oxygen material is a material with good cycling stability (the capacity retention rate is still more than 80% when the cycle is more than 500 times), high capacity (1500-.

However, the silicon-oxygen material has a high irreversible capacity, so that the first coulombic efficiency of the silicon-oxygen material is generally lower than 75%, which has been the biggest obstacle limiting the application of the silicon-oxygen material. The first coulombic efficiency of the silica material can be greatly improved by carrying out pre-lithiation on the silica material, and can reach more than 90% by optimizing the pre-lithiation amount.

Currently, in the preparation of a negative electrode, water is generally used as a solvent to disperse a negative active material in consideration of environmental protection, cost, safety, and the like. In order to obtain a good dispersion effect, means such as high-intensity kneading or high-speed dispersion are generally used during processing, which inevitably damages a material having low water-resistant stability. The buffer phase in the prelithiated silica material is typically composed of a mixture of a series of silicates (e.g., Li)₂SiO₃、Li₆Si₂O₇、Li₂Si₂O₅、Li₄SiO₄) And (4) forming. These silicates are not highly water-resistant and undergo hydrolytic polymerization in aqueous systems to produce a series of silica clusters. These silica clusters are highly susceptible to further polymerization by acid-base fluctuations in the slurry system, resulting in gelation.

On the other hand, when the negative electrode is prepared, water is usually used as a solvent to prepare slurry, and a binder or a dispersant is required to wet the material through the action of high-speed shearing force in the preparation process of the slurry, so that the overall structure of the negative electrode active material is seriously damaged, silicon nanoparticles with high reactivity of a silicon-oxygen material in the negative electrode active material are exposed, the silicon-oxygen material is easier to contact with water and generate hydrogen, the capacity and the cycle stability of the silicon-oxygen material are seriously reduced, and the storage stability and the safety of the aqueous slurry are seriously influenced by the hydrogen generated in the large-scale preparation of the aqueous slurry of the negative electrode active material.

In order to overcome the foregoing problems, the present application provides a high water resistance negative active material to satisfy the conventional aqueous processing process. Firstly, hydrolyzing an inorganic coating material on the surface of a silica material to generate an M-O group (M comprises at least one of aluminum element, boron element and phosphorus element) which is more easily combined with the surface of the silica material, and further dehydrating and polymerizing the group and silanol groups on the surface of the silica material, thereby forming a network-shaped compact coating layer which takes Si-O-M as the main component on the surface of the silica material. Then the hydrophobic polymer is coated to form a water-resisting layer on the surface of the silicon-oxygen material, so that the whole structure has higher water-resisting stability. The cathode active material can meet the processing requirement of aqueous slurry in the traditional cathode manufacturing. In addition, the negative electrode active material has high water-resistant stability, and can keep high first coulombic efficiency.

Third, negative pole

The embodiment of the application provides a negative electrode. The negative electrode includes a current collector and a negative active material layer on the current collector. The negative active material layer includes a negative electrode material according to an embodiment of the present application.

In some embodiments, the negative active material layer includes a binder. In some embodiments, the adhesive includes, but is not limited to: polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene 1, 1-difluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, or nylon.

In some embodiments, the negative active material layer includes a conductive material. In some embodiments, the conductive material includes, but is not limited to: natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, metal powder, metal fiber, copper, nickel, aluminum, silver, or polyphenylene derivative.

In some embodiments, the current collector includes, but is not limited to: copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, or a polymer substrate coated with a conductive metal.

In some embodiments, the negative electrode may be obtained by: the active material, the conductive material, and the binder are mixed in a solvent to prepare an active material composition, and the active material composition is coated on a current collector.

In some embodiments, the solvent may include, but is not limited to: n-methyl pyrrolidone.

Fourth, positive electrode

Materials, compositions, and methods of making positive electrodes useful in embodiments of the present application include any of the techniques disclosed in the prior art. In some embodiments, the positive electrode is the positive electrode described in U.S. patent application No. US9812739B, which is incorporated by reference herein in its entirety.

In some embodiments, the positive electrode includes a current collector and a positive active material layer on the current collector.

In some embodiments, the positive active material includes, but is not limited to: lithium cobaltate (LiCoO)₂) Lithium Nickel Cobalt Manganese (NCM) ternary material and lithium iron phosphate(LiFePO4) or lithium manganate (LiMn2O 4).

In some embodiments, the positive active material layer further includes a binder, and optionally a conductive material. The binder improves the binding of the positive electrode active material particles to each other, and also improves the binding of the positive electrode active material to the current collector.

In some embodiments, the adhesive includes, but is not limited to: polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene 1, 1-difluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, or the like.

In some embodiments, the conductive material includes, but is not limited to: carbon-based materials, metal-based materials, conductive polymers, and mixtures thereof. In some embodiments, the carbon-based material is selected from natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, or any combination thereof. In some embodiments, the metal-based material is selected from metal powder, metal fiber, copper, nickel, aluminum, or silver. In some embodiments, the conductive polymer is a polyphenylene derivative.

In some embodiments, the current collector may include, but is not limited to: aluminum.

The positive electrode may be prepared by a preparation method well known in the art. For example, the positive electrode can be obtained by: the active material, the conductive material, and the binder are mixed in a solvent to prepare an active material composition, and the active material composition is coated on a current collector. In some embodiments, the solvent may include, but is not limited to: n-methyl pyrrolidone.

Fifth, electrolyte

The electrolyte that may be used in the embodiments of the present application may be an electrolyte known in the art.

In some embodiments, the electrolyte includes an organic solvent, a lithium salt, and an additive. The organic solvent of the electrolyte according to the present application may be any organic solvent known in the art that can be used as a solvent of the electrolyte. The electrolyte used in the electrolyte according to the present application is not limited, and may be any electrolyte known in the art. The additive of the electrolyte according to the present application may be any additive known in the art as an additive of electrolytes.

In some embodiments, the organic solvent includes, but is not limited to: ethylene Carbonate (EC), Propylene Carbonate (PC), diethyl carbonate (DEC), Ethyl Methyl Carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate or ethyl propionate.

In some embodiments, the lithium salt comprises at least one of an organic lithium salt or an inorganic lithium salt.

In some embodiments, the lithium salt includes, but is not limited to: lithium hexafluorophosphate (LiPF)₆) Lithium tetrafluoroborate (LiBF)₄) Lithium difluorophosphate (LiPO)₂F₂) Lithium bis (trifluoromethanesulfonylimide) LiN (CF)₃SO₂)₂(LiTFSI), lithium bis (fluorosulfonyl) imide Li (N (SO)₂F)₂) (LiFSI), lithium bis (oxalato) borate LiB (C)₂O₄)₂(LiBOB) or lithium difluorooxalato borate LiBF₂(C₂O₄)(LiDFOB)。

In some embodiments, the concentration of lithium salt in the electrolyte is: about 0.5 to 3mol/L, about 0.5 to 2mol/L, or about 0.8 to 1.5 mol/L.

Sixth, the barrier film

In some embodiments, a separator is provided between the positive and negative electrodes to prevent short circuits. The material and shape of the separation film that can be used for the embodiment of the present application are not particularly limited, and may be any of the techniques disclosed in the prior art. In some embodiments, the separator includes a polymer or inorganic substance or the like formed of a material stable to the electrolyte of the present application.

For example, the release film may include a substrate layer and a surface treatment layer. The substrate layer is a non-woven fabric, a film or a composite film with a porous structure, and the material of the substrate layer is at least one selected from polyethylene, polypropylene, polyethylene terephthalate and polyimide. Specifically, a polypropylene porous film, a polyethylene porous film, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite film can be used.

At least one surface of the substrate layer is provided with a surface treatment layer, and the surface treatment layer can be a polymer layer or an inorganic layer, or a layer formed by mixing a polymer and an inorganic substance.

The inorganic layer comprises inorganic particles and a binder, wherein the inorganic particles are selected from one or more of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium oxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide and barium sulfate. The binder is selected from one or a combination of more of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoropropylene.

The polymer layer comprises a polymer, and the material of the polymer is selected from at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride or poly (vinylidene fluoride-hexafluoropropylene).

Seventh, electrochemical device

Embodiments of the present application provide an electrochemical device including any device in which an electrochemical reaction occurs.

In some embodiments, the electrochemical device of the present application includes a positive electrode sheet having a positive active material capable of occluding and releasing metal ions; a negative electrode according to an embodiment of the present application; an electrolyte; and a separator interposed between the positive electrode and the negative electrode.

In some embodiments, the electrochemical devices of the present application include, but are not limited to: all kinds of primary batteries, secondary batteries, fuel cells, solar cells or capacitors.

In some embodiments, the electrochemical device is a lithium secondary battery.

In some embodiments, the lithium secondary battery includes, but is not limited to: a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

Eight, electronic device

The electronic device of the present application may be any device using the electrochemical device according to the embodiment of the present application.

In some embodiments, the electronic devices include, but are not limited to: a notebook computer, a pen-input computer, a mobile computer, an electronic book player, a cellular phone, a portable facsimile machine, a portable copier, a portable printer, a headphone, a video recorder, a liquid crystal television, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic organizer, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, an automobile, a motorcycle, a power-assisted bicycle, a lighting apparatus, a toy, a game machine, a clock, an electric tool, a flashlight, a camera, a large-sized household battery or a lithium ion capacitor, and the like.

Taking a lithium ion battery as an example and describing the preparation of the lithium ion battery with reference to specific examples, those skilled in the art will understand that the preparation method described in the present application is only an example, and any other suitable preparation method is within the scope of the present application.

Examples

The following describes performance evaluation according to examples and comparative examples of lithium ion batteries of the present application.

Preparation of negative active material

Negative active materials of examples 1 to 18 were prepared as follows:

(1) prelithiated silica material (C%: about 3.2%, Dv50 ═ about 5.1 μm, silicon grain size about 5nm, buffer phase Li₂SiO₃) Adding the pre-lithiated silica material and the inorganic coating material into ethanol, stirring for about 0.5-4h until a uniform suspension is formed, filtering the formed suspension, and drying the filtered substance at about 80 ℃ for about 12h to obtain the pre-lithiated silica material with the surface coated by the inorganic coating layer;

(2) the pre-lithiated silica material whose surface is coated with an inorganic coating layer and the polymer obtained above are added to ethanol to form a suspension, and then the solvent is removed from the formed suspension, followed by heating the filtered material at about 150 ℃ for about 10 hours to obtain a negative electrode active material of the present application.

The method of preparing the negative active material in comparative example 1 is similar to the above-described method of preparing, except that the prelithiated silicon oxygen material in comparative example 1 is not coated with an inorganic material, but is directly coated with a polymer.

The method of preparing the negative active material in comparative example 2 is similar to the above-described method of preparing, except that the prelithiated silicon oxygen material in comparative example 2 is only coated with an inorganic material, and is not coated with a polymer.

The negative active material in comparative example 3 was a pre-lithiated silica material that was not subjected to any coating.

Second, testing method

1. Method for measuring content of M element in negative electrode active material

About 0.2g of the negative electrode active material was weighed and placed in a Polytetrafluoroethylene (PTFE) beaker, and the weight of the sample was recorded to the nearest 0.0001g after the digital balance measurement was stabilized. To the sample was slowly added about 10mL of concentrated HNO₃And about 2mL of HF, placed on a plate heater at about 220 ℃ and heated to digest it to almost dry. Slowly add about 10mL nitric acid and continue heating to digest for about 15min, allowing the sample to dissolve well. The dissolved sample was placed in a fume hood and cooled to room temperature. The sample solution was shaken up and slowly poured into a funnel with a single layer of filter paper and the beaker and filter residue were rinsed 3 times. The volume is adjusted to about 50mL at about 20 +/-5 ℃ and the mixture is shaken up. And testing the ion spectrum intensity of the filtrate by using an Inductively Coupled Plasma (ICP) emission spectrometer (PE 7000), and calculating the ion concentration of the filtrate according to the standard curve, thereby calculating the content of the elements contained in the sample.

2. Method for testing content of polymer coating layer in negative electrode active material

The content of the polymer coating layer in the negative electrode active material may be performed by thermogravimetric analysis (TGA).

3. X-ray diffraction characterization method of negative electrode active material

A sample of the negative active material was placed in a circular pit having a diameter of about 1cm, the surface was scraped off, and the sample was scanned by an X-ray spectrometer (D8 Advance, Cu target X-ray source) at an inclination angle 2 θ of from about 10 ° to about 85 ° and a scanning frequency of 3 °/min.

4. Method for evaluating sedimentation condition of aqueous slurry of negative electrode active material

The negative electrode active material, conductive carbon black and binder PAA (modified polyacrylic acid, PAA) obtained in example or comparative example were mixed in a weight ratio of about 80: 10: 10, adding the mixture into deionized water, and stirring to form aqueous slurry. The aqueous slurry was stored for about 48 hours and the final viscosity of the aqueous slurry was measured. Comparing the final viscosity to the initial viscosity and noting no sedimentation when the viscosity decreases less than about 1000Pa · s; slight settling was noted when the viscosity decreased between about 1000-2000 Pa.s; when the viscosity decreased more than about 2000 pas, severe sedimentation was noted.

5. Method for evaluating gelation of aqueous slurry of negative electrode active material

The negative electrode active material, conductive carbon black and binder PAA (modified polyacrylic acid, PAA) obtained in example or comparative example were mixed in a weight ratio of about 80: 10: 10, adding the mixture into deionized water, and stirring to form aqueous slurry. The aqueous slurry was stored for about 48 hours and the lower layer of the aqueous slurry was tested for particle condition by dynamic light scattering. Slight gelation was noted when particles with a particle size of about 50-100 μm appeared in the aqueous slurry; severe gelation is noted when particles with a particle size greater than about 100 to about 1000 μm appear in the aqueous slurry.

6. Method for measuring gas production rate of negative electrode active material aqueous slurry

The negative electrode active material, conductive carbon black and binder PAA (modified polyacrylic acid, PAA) obtained in example or comparative example were mixed in a weight ratio of about 80: 10: 10, adding the mixture into deionized water, and stirring to form aqueous slurry. About 100g of the aqueous slurry was sealed in about 250mL of a closed container for about 48 hours. The proportion of hydrogen it produces was tested by gas chromatography. According to the reaction principle, other gases in the system are basically unchanged, and the gas production is characterized by the volume ratio of hydrogen in the whole mixed system under the condition of only generating hydrogen.

7. The button cell testing method comprises the following steps:

under dry argon atmosphere, LiPF is added into a solvent formed by mixing Propylene Carbonate (PC), Ethylene Carbonate (EC) and diethyl carbonate (DEC) (the weight ratio is about 1: 1: 1)₆Mixing uniformly, wherein LiPF₆Was added with about 7.5 wt% of fluoroethylene carbonate (FEC), and mixed uniformly to obtain an electrolyte solution.

The negative electrode active materials, conductive carbon black and a binder PAA (modified polyacrylic acid, PAA) obtained in examples and comparative examples were mixed in a weight ratio of 80: 10: 10 adding the mixture into deionized water, stirring to form slurry, coating by using a scraper to form a coating with the thickness of about 100 mu m, drying at about 85 ℃ for about 12 hours in a vacuum drying oven, cutting into round pieces with the diameter of about 1cm by using a punch in a drying environment, taking a metal lithium piece as a counter electrode in a glove box, selecting a ceglard composite film as an isolating film, and adding electrolyte to assemble the button cell. The battery is subjected to charge and discharge tests by using a blue electricity (LAND) series battery test, and the first coulombic efficiency of the battery is the ratio of the charge capacity to the discharge capacity.

8. Lithium ion battery cycle performance test

(1) Preparation of lithium ion battery

Preparation of the Positive electrode

Subjecting LiCoO to condensation₂The conductive carbon black and polyvinylidene fluoride (PVDF) are fully stirred and uniformly mixed in an N-methyl pyrrolidone solvent system according to the weight ratio of about 95 percent to 2.5 percent to prepare the anode slurry. And coating the prepared anode slurry on an anode current collector aluminum foil, drying and cold pressing to obtain the anode.

Preparation of the negative electrode

Graphite, negative electrode active materials prepared according to examples 1 to 18 and comparative examples 1 to 3, and a conductive agent (conductive carbon black, Super)

) And binder PAA in a weight ratio of about 70%: 15%: 5%: 10%, adding an appropriate amount of water, and kneading at a solid content of about 55% to 70%. Adding a proper amount of water, and adjusting the viscosity of the slurry to about 4000-6000 Pa.s to prepare the cathode slurry.

And coating the prepared negative electrode slurry on a negative electrode current collector copper foil, drying and cold pressing to obtain a negative electrode.

Preparation of the electrolyte

Under dry argon atmosphere, LiPF is added into a solvent formed by mixing Propylene Carbonate (PC), Ethylene Carbonate (EC) and diethyl carbonate (DEC) (the weight ratio is about 1: 1: 1)₆Mixing uniformly, wherein LiPF₆The concentration of (A) was about 1.15mol/L, and about 7.5 wt% of fluoroethylene carbonate (FEC) was further added thereto and mixed uniformly to obtain an electrolyte solution.

Preparation of the separator

The PE porous polymer film is used as a separation film.

Preparation of lithium ion battery

The anode, the isolating film and the cathode are sequentially stacked, and the isolating film is positioned between the anode and the cathode to play a role in isolation. And winding to obtain the naked electric core. And arranging the bare cell in an external package, injecting electrolyte and packaging. The lithium ion battery is obtained through the technological processes of formation, degassing, edge cutting and the like.

(2) And (3) testing the cycle performance:

charging to 4.4V at constant current of 0.7C and charging to 0.025C at constant voltage at 25 deg.C, and standing for 5 min. Then discharged to 3.0V at 0.5C. And taking the capacity obtained in the step as an initial capacity. And (3) carrying out a cycle test by using 0.7C charging/0.5C discharging, taking the ratio of the capacity of each step to the initial capacity, and carrying out small current recovery every 50 circles (0.2C constant current charging to 4.4V, constant voltage charging to 0.025C, standing for 5 minutes, and 0.2C discharging to 3.0V) to obtain a capacity decay curve.

Table 1 lists the materials and amounts used in the examples and comparative examples, as well as the results of the tests.

TABLE 1

"-" indicates the absence of the substance.

As can be seen from fig. 2B, the negative electrode material of comparative example 2 has an inorganic coating layer on the surface. As can be seen from fig. 2C, the surface of the negative electrode material of example 12 has a polymer coating layer. As can be seen from fig. 2D, the anode material of example 12 has a double-layered coated surface structure, i.e., the pre-lithiated silica material is coated with both the inorganic coating layer and the polymer coating layer.

It can be seen from the test results of comparative example 3 that aqueous slurries made from pre-lithiated silicone materials exhibit severe settling, severe gelling and severe gassing without inorganic and polymeric coating layers.

It can be seen from the test results of comparative example 2 that the aqueous slurry of pre-lithiated silica material with inorganic coating layer exhibited slight settling, slight gelling and severe gassing. The above results indicate that the inorganic coating layer can improve the water-resistant stability of the prelithiated silica material.

It can be seen from the test results of comparative example 1 that the aqueous slurry of pre-lithiated silicone material with polymer coating layer exhibited slight settling, slight gelling and severe gassing. The above results indicate that the polymer coating layer can improve the water-resistant stability of the prelithiated silicone material.

Examples 1-18, which simultaneously coat the surface of the pre-lithiated silica material with an inorganic coating layer and a polymer coating layer, significantly improve the settling, gelation, and/or gassing of an aqueous slurry of the pre-lithiated silica material as compared to comparative examples 1-3. As shown in fig. 3A, the aqueous slurry made of the negative active material of comparative example 3 generated severe sedimentation and severe gelation phenomena, while, as shown in fig. 3B, the aqueous slurry made of the negative active material of example 12 did not generate sedimentation and gelation phenomena.

Fig. 4 shows cycle decay curves of the lithium ion batteries of comparative example 2, comparative example 3 and example 12 of the present application, respectively, wherein three cycle decay curves of example 12 were obtained by testing three lithium ion batteries prepared according to example 12 under the same test conditions; the two cycle decay curves of comparative example 2 were obtained by testing two lithium ion batteries prepared according to comparative example 2 under the same test conditions; and comparative example 3 two cycle decay curves were obtained by testing two lithium ion batteries prepared according to comparative example 3 under the same test conditions. As shown in fig. 4, the cycle stability of the negative electrode material can be significantly improved by coating the surface of the pre-lithiated silicon oxide material with an inorganic coating layer and a polymer coating layer at the same time.

As can be seen from the test results of examples 10 to 12, the gas evolution of the aqueous slurry made of the negative electrode material was significantly improved as the amount of the inorganic coating material was increased. The result shows that the increase of the content of the inorganic coating layer is beneficial to improving the water-resistant stability of the cathode material.

From the test results of examples 12, 17 and 18, it can be seen that the gel condition and the gassing condition of the aqueous slurry made of the anode material are significantly improved as the polymer content increases. The results show that the increase of the polymer content is beneficial to improving the water-resistant stability of the negative electrode material.

Reference throughout this specification to "some embodiments," "one embodiment," "another example," "an example," "a specific example," or "some examples" means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present application. Thus, throughout the specification, descriptions appear, for example: "in some embodiments," "in an embodiment," "in one embodiment," "in another example," "in one example," "in a particular example," or "by example," which do not necessarily refer to the same embodiment or example in this application. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

Although illustrative embodiments have been illustrated and described, it will be appreciated by those skilled in the art that the above embodiments are not to be construed as limiting the application and that changes, substitutions and alterations can be made to the embodiments without departing from the spirit, principles and scope of the application.

Claims

1. An anode material comprising a lithiated silica material, an inorganic coating layer, and a polymer coating layer, wherein the inorganic coating layer and the lithiated silica material have at least a Si-O-M bond therebetween, wherein M includes at least one of an aluminum element, a boron element, and a phosphorus element, wherein the lithiated silica material comprises nano-silicon crystal grains having a grain size of not greater than 10 nm.

2. The anode material of claim 1, wherein the lithiated silica material comprises Li₂SiO₃、Li₆Si₂O₇、Li₂Si₂O₅And Li₄SiO₄At least one of (1).

3. The anode material according to claim 1, wherein the inorganic coating layer comprises a compound containing at least one of a phosphorus element, an aluminum element, and a boron element.

4. The anode material of claim 1, wherein the weight percentage of M is 0.05 wt% to 1.0 wt% based on the total weight of the anode material.

5. The anode material according to claim 1, wherein the anode active material has an X-ray diffraction peak having a 2 Θ value of 21.7 ± 1 °.

6. The negative electrode material of claim 1, wherein the polymer coating comprises a hydrophobic polymer.

7. The negative electrode material of claim 1, wherein the polymer coating layer comprises at least one of the following compounds: polyimide, polyamideimide, polysiloxane, poly (styrene-butadiene rubber), epoxy resin, polyester resin, and polyurethane resin.

8. The anode material of claim 1, wherein the weight percentage of the polymer cladding is 0.1 wt% to 10 wt% based on the total weight of the anode material.

9. The anode material of claim 1, wherein the polymer cladding layer has a thickness of 5nm to 200 nm.

10. The anode material of claim 1, the nano-silicon grains having a grain size of no greater than 8 nm.

11. An anode comprising a substrate and the anode material of any one of claims 1-10.

12. An electrochemical device comprising a cathode and the anode of claim 11.

13. An electronic device comprising the electrochemical device of claim 12.